MANITOWOC – Manitowoc County Historical Society members thought they were in for a potentially explosive day recently, but it turned out to be a dud.

And they're OK with that.

When a volunteer was searching for war memorabilia at the Heritage Center to use in an upcoming display, she looked inside a rarely opened basement cabinet and found a box with a military hand grenade and mortar round, both of which appeared might still be live.

"When I first heard about it, I was incredibly terrified because it's right below my office," said Amy Meyer, executive director of the historical society. "Even though it's been there for a long time, I was worried the movement we had done … touching the box, would have jarred it or made it be less stable."

Staff was aware historic memorabilia that still needed to be recorded into the museum's collection was stored in the cabinet.

"We knew there was war stuff in there, just never opened the doors to figure out what," Meyer said. "Now we know."

Meyer said she assumes the box, which also contained gas masks and canteens, probably was donated and previous volunteers put it in the cabinet for safe keeping with the intention to catalog it later.

"The Manitowoc County Historical Society inventories all artifacts as they are added to our historical collection," she said. "The items found in the cabinet were likely there for some time and were found and handled in a safe manner."

Meyer estimates the grenade and mortar round date back to World War II or earlier and have been in the museum's possession for about a decade.

No one at the museum attempted to touch the items, and instead contacted the Brown-Outagamie Bomb Squad.

"We were going on the assumption it was live because there weren't any indications on the grenade itself either by the color or a drilled out hole on the bottom," Meyer said.

Lt. Chris Knurr of the bomb squad said officers treated the ammunition as if it was live and took proper precautions to handle and transport them. The grenade and mortar round were taken to the Brown County Sheriff's Department where they were X-rayed.

"We can tell by the interior of it," Knurr said. "When we X-rayed (the grenade), you could actually see the cap was fired, or the fuse I should say. So we just unscrewed it and … it was hollow, so that's the sign of a training grenade."

Meyer said the volunteers correctly dealt with the situation to ensure the safety of others and used it as a good learning opportunity.

"This is just showing history is really cool. It's not just things in dusty history books," she said. "The society's historical archives collection includes thousands of images and objects that serve as wonderful physical reminders of our heritage."

Meyer is now planning to go through seldom-visited storage spaces at the 50-year-old Pinecrest Historical Village this spring to rediscover other hidden treasures.

"Even though the items weren't live, this was a great example of how searching through pieces of our past can be exciting," Meyer said. "History is a blast."